Battery pack having communication terminal isolation function

ABSTRACT

A battery pack including a communication terminal insulation function with an external system connected to the battery pack and a control method thereof.

TECHNICAL FIELD

The present invention relates to a battery pack, and more particularly,to a battery pack including a communication terminal insulation functionwith an external system connected to the battery pack.

BACKGROUND ART

Generally, various portable electronic devices (hereinafter, referred toas ‘external systems’) including a notebook computer, a mobile phone,and a camera are equipped with a battery pack including a plurality ofbattery cells capable of charge and discharge.

The battery pack is provided with an external terminal including acommunication stage. The battery pack is connected to an external systemthrough which the battery cells included in the battery pack are chargedand discharged, and are communicated with the external system.

On the other hand, if the communication terminal to which the batterypack and the external system are communicatively connected is notinsulated, in a case where the protection operation of the battery pack,specifically, the flow of the discharge current is blocked, a surgecurrent is generated, and the generated surge current may flow into theexternal system through the communication terminal, which may adverselyaffect the external system.

In addition, this may destroy the microcomputer unit (MCU) which flowsinto the battery pack through the communication terminal as well as theexternal system to perform the overall control function of the batterypack, and therefore, there arises a problem in controlling the normaloperation of the battery pack, which results in a safety problem of thebattery pack.

In order to prevent such a problem from occurring, the communicationterminal between the battery pack and the external system must beinsulated, but for this, since separate components to perform theisolation function, for example an Isolator IC, must be additionallyconfigured to ensure that the terminals are isolated, there is a problemthat extra cost is incurred due to the additional parts.

DISCLOSURE OF THE INVENTION Technical Problem

The present invention is to provide a method capable of performingcommunication isolation processing without incurring any additionalcosts.

Technical Solution

In accordance with an exemplary embodiment, a battery pack includes: acell balancing unit for balancing a plurality battery cells; an analogfront end (AFE) for monitoring a voltage state of each of the batterycells and controlling the cell balancing unit; a microcomputer unit(MCU) for controlling the AFE based on a voltage state of each batterycell monitored by the AFE; and an external terminal connected to thebattery pack and an external system.

The external terminal may include: an output terminal for allowing acurrent to flow between the battery cell and the external system; and acommunication terminal for enabling communication between the MCU andthe external system.

The battery pack may further include: a charge field effect transistor(FET) for blocking current flow from the output terminal to the batterycell; and a discharge FET for blocking current flow from the batterycell to an output terminal, which are configured on a current pathbetween the battery cell and the output terminal.

The charge FET and the discharge FET may be turned on/off by the AFE.

A communication path may be formed between the MCU and the communicationterminal, and a communication control FET for blocking a path betweenthe communication terminal and the MCU under a control of the MCU may beconfigured on the communication path.

The MCU may include: an overcharge determination unit for generating anovercharge determination signal and outputting the overchargedetermination signal to the AFE, when it is determined that the batterycell is overcharged; an overdischarge determination unit for generatingan overdischarge determination signal and outputting the overdischargedetermination signal to the AFE, when it is determined that the batterycell is overdischarged; and a communication control FET block unit fordetecting that the overdischarge determination signal outputted from theoverdischarge determination unit and outputting a communication controlFET off signal to the communication control FET to block a current flowbetween the MCU and the communication terminal.

When an overcharge determination signal is inputted from the MCU, theAFE may output a charge FET off signal to block a flow of a chargecurrent, and when the overdischarge determination signal is inputted,the AFE may output a discharge FET off signal to block a flow of adischarge current.

The discharge FET off signal may be outputted after a predetermined timeafter the communication control FET off signal is outputted.

In accordance with an exemplary embodiment, a method of controlling abattery pack including battery cells, the method comprising: a statedetermination step of monitoring a voltage state of each battery cell todetermine an overcharge or overdischarge state of battery cells, whereinwhen it is determined that the battery cells are overdischarged in thestate determination step, an overdischarge protection step is operated,wherein the overdischarge protection step includes: an overdischargedetermination signal output step of outputting an overdischargedetermination signal to an AFE to block a flow of a discharge current; acommunication control FET block step of blocking a communication controlfield effect transistor (FET) configured on a communication path betweenthe battery pack and an external system; and a discharge FET block stepof blocking a flow of a discharge current from the battery cells to anexternal terminal.

The method may further include, after the operation of the overdischargeprotection step, an overdischarge release determination step ofmonitoring the voltage state of each battery cell to determine whetheroverdischarge of battery cells is released, wherein when it isdetermined that the overdischarge state of the battery cells isreleased, an overdischarge release step of releasing an overdischargeprotection state of the battery cells may be operated, wherein theoverdischarge release step may include: a discharge FET block releasestep of generating and outputting a FET on signal to release thedischarge FET block; and a communication control FET block release stepof generating and outputting the communication control FET on signal torelease the communication control FET block, wherein the communicationcontrol FET block release step may be operated a predetermined timeafter the discharge FET block release step is operated.

The discharge FET block step may be operated a predetermined time afterthe communication control FET block step is operated.

Advantageous Effects

The present invention is advantageous in that it may be applied to alow-cost product because it does not incur any additional cost byenabling a communication terminal insulation process using a circuitgenerally constituted in a battery pack.

In addition, the MCU of the battery pack may be protected so that it mayprovide improved stability of the battery pack.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing a configuration of a battery packaccording to the present invention; and

FIG. 2 is a block diagram showing a method of controlling a battery packaccording to the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings so that those skilledin the art may easily carry out the present invention. The presentinvention may, however, be embodied in different forms and should not beconstructed as limited to the embodiments set forth herein. Parts notrelating to description are omitted in the drawings in order to clearlydescribe the present invention and like reference numerals refer to likeelements throughout.

Although the terms “initial,” “second,” etc., may be used herein todescribe various elements, these elements should not be limited by theseterms. The above terms are used only to distinguish one component fromanother. For example, an initial component may be referred to as asecond component and vice versa without departing from the scope of thepresent invention. Terms used in this specification are used to describespecific embodiments, and are not intended to limit the scope of thepresent invention. The singular expressions include plural expressionsunless the context clearly dictates otherwise.

Throughout the specification, when a portion is referred to as being“connected” to another portion, it includes not only “directlyconnected” but also “electrically connected” with another elementtherebetween. Furthermore, when it is described that one comprises (orincludes or has) some elements, it should be understood that it maycomprise (or include or has) only those elements, or it may comprise (orinclude or have) other elements as well as those elements if there is nospecific limitation. The term “˜ing operation” or “operation of ˜ing”used throughout the specification does not mean “operation for ˜ing”.

Terms used in this specification may be currently widely used generalterms in consideration of functions in the present invention but mayvary according to the intents of those skilled in the art, precedents,or the advent of new technology. Additionally, in certain cases, theremay be terms the applicant selects arbitrarily and in this case, theirmeanings are described in a corresponding description part of thepresent invention. Accordingly, terms used in the present inventionshould be defined based on the meaning of the term and the entirecontents of the present invention instead of the simple term name.

Hereinafter, the present invention will be described in detail withreference to the drawings, and in the following description, the analogfront end will be referred to as an abbreviation “AFE” and themicrocomputer unit will be referred to as an “MCU” for the sake ofconvenience.

FIG. 1 is a circuit diagram briefly showing a configuration of a batterypack according to the present invention.

Referring to FIG. 1, a battery pack 100 includes a battery cell 110, acell balancing unit 120, an AFE 130, an MCU 140, an external terminal150, a charge FET 160, a discharge FET 170, and a communication controlFET 180.

Here, the external terminal 150 is configured to connect the batterypack 100 and the external system 200, and the external system 200 maybe, for example, a device capable of attaching/detaching a battery pack,such as a notebook computer, a mobile phone, and a camera.

Accordingly, the battery cells 110 may be charged or discharged throughthe external terminal 150 by connecting a power supply device such as anadapter (charge unit) or an external load device to the external system200.

Such an operation will be described in detail in the description of theexternal terminal 150.

Here, the AFE and the MCU may be an integrated circuit.

The battery cell 110 is charged and discharged under the control of theMCU 140, and although shown as a block in the drawings for the sake ofconvenience, the battery cell 110 may include one or more battery cellsconnected in series or in parallel.

The cell balancing unit 120 may be connected to the plurality of batterycells 110 to perform cell balancing. The cell balancing unit 120 mayperform balancing so that the voltages of the battery cells 110 arebalanced by the AFE 130, and more precisely, may perform the balancingoperation under the control of the MCU 140 that controls the operationof the AFE 130 as a whole.

Here, the cell balancing unit 120 may include a voltage sensing unitconnected to each of the battery cells 110 to sense a voltage, or mayhave a separate configuration. The voltage sensing unit (not shown) maysense the voltage of each battery cell 110 and provide the informationto the AFE 130, which will be described later.

The AFE 130 may periodically receive the voltage information of each ofthe sensed battery cells 110 to monitor the voltage state of the batterycells 110.

Also, the AFE 130 transmits information on the voltage state of themonitored battery cells 110 to the MCU 140, and in response to thecontrol command of the MCU 140 that receives the information, the AFE130 may operate the cell balancing unit 120 to turn on and off thecharge FET 160 and the discharge FET 170 and balance the voltages of thebattery cells 110.

In other words, as shown in the drawings, the AFE 130 is configuredbetween the battery cells 110/the cell balancing unit 120 and the MCU130 so that it operates the charge and discharge FETs 160 and 170 andthe cell balancing unit 120 under the overall control of the MCU 130.

As described above, the MCU 140 receives information on the voltagestate of the battery cells 110 from the AFE 130 and controls charge anddischarge and cell balancing operations of the battery cells 110 basedon the information.

More precisely, the MCU 140 provides control signals/commands to performcharge and discharge and cell balancing operations according to thevoltage state of battery cells 110, and the AFE 130 receiving thecontrol signal/command operates the charge FET 160, the discharge FET170 and the cell balancing unit 120 in response to the controlsignal/command.

The MCU 140 may compare the voltage state of each battery cell 110received from the AFE 130 with a predetermined determination value todetermine whether the battery cell 110 is overcharged or overdischarged.It may be configured including an overcharge determination unit 142 for,if the voltage of the battery cell 110 is equal to or higher than thepredetermined overcharge determination value, determining it as anovercharge state, generating an overcharge determination signalcorresponding thereto, and outputting the overcharge determinationsignal to the AFE 130.

In addition, it may be configured including an overcharge determinationunit 144 for, if the voltage of the battery cell 110 is equal to or lessthan the predetermined overcharge determination value, determining it asan overdischarge state, generating an overdischarge determination signalcorresponding thereto, and outputting the overdischarge determinationsignal to the AFE 130.

Therefore, if an overcharge determination signal is inputted, in orderto prevent further charging current from entering the battery pack, theAFE 130 may turn off the charge FET 160, and if an overdischargedetermination signal is inputted, the AFE 130 may turn off the dischargeFET 170 to block the flow of the discharge current of the battery pack.

Also, the MCU 140 may communicate with the external system 200 and thebattery pack 100. The MCU 140 may communicate with an external system200 connected to an external terminal 150 through an SMBUS formedtherein, and for example, the MCU 140 transmits cell data such as avoltage state of the battery cells 110 received from the AFE 130 to theexternal system 200 through a communication path formed between the MCU140 and the external terminal 150.

At this time, the cell data may be transmitted from the SMBUS to theexternal system 200 in synchronization with the clock signal CLK of thecommunication terminal through the communication paths (first and secondpaths).

On the other hand, the MCU 140 may be configured including acommunication control FET block unit 146 for controlling on/off of thecommunication control FET 180 formed in the communication path betweenthe MCU 140 and the communication terminal 154 of the external terminal150. This will be described in detail in the description of thecommunication control FET 180.

Meanwhile, the external terminal 150 may be configured including anoutput terminal 152 and a communication terminal 154, as shown in thedrawing.

The output terminal 152 may be charge and discharge paths with anexternal system 200 that allows the battery cells 110 to be charged anddischarged. That is, current flows through each path between the batterycells 110 and P+ and P− of the output terminal 150, so that the batterycells 110 may be charged and discharged. That is, this path may bedescribed as a charge/discharge path.

For example, when an adapter (charge unit) for supplying the voltage isconnected to the external system 150 connected to the external terminal150 of the battery pack 100, a charge current flows through the outputterminal 152 so that the battery cells 110 are charged.

On the other hand, when the external system 150 and the adapter (chargeunit) are separated and connected to the external load, a current flowsfrom the battery cells 110 to the external load of the external system200 through the output terminal 152 of the external terminal 150, sothat the battery cells 110 are discharged.

At this time, the charge FET 160 and the discharge FET 170 areconfigured on the charge/discharge path formed between the battery cells110 and the output terminal 152, and as described above, under thecontrol of the MCU 140, the AFE 130 turns on/off the charge FET 160 andthe discharge FET 170 so that the charge and discharge operations of thebattery cells may be controlled.

That is, as described above, when the MCU 140 outputs an overchargedetermination signal, the AFE 130 outputs an off signal to the chargeFET 160 to block the charge current from flowing into the battery cells110 from the adapter (charge unit) of the external system 200, and whenan overdischarge determination signal is outputted from the MCU 140, theAFE 130 outputs an off signal to the discharge FET 170 to block the flowof the current from the battery cells 110 to the external load of theexternal system 200, that is, the flow of the discharge current.

Also, when the overcharge state of the battery cells is released, thecharge FET 160 is turned on, and when the overdischarge state isreleased, the battery cells are allowed to be charged and dischargedthrough control to turn on the discharge FET 170.

Here, the charge FET 160 and the discharge FET 170 are connected on asingle path, and the direction of current flow is opposite to eachother, thereby limiting the flow of charge and discharge current.

On the other hand, the communication terminal 154 may be a path for theMCU 140 to transmit data of the battery cells 110 to the external system200, for example, voltage state information and the like.

A communication path for communication of the external system 200 isformed between the MCU 140 and the communication terminal 154, and thedata of the battery cells 110 may be transferred from the MCU 140 to theexternal system 200 through the communication path of the externalsystem 200 connected thereto.

At this time, the communication control FET 180 for blocking the currentflow from the communication terminal 154 to the MCU 140 may beconfigured on the communication path between the MCU 140 and thecommunication terminal 154.

More specifically, as shown in the drawing, the first and second pathsmay be respectively connected to the Clock (C) terminal and the Date (D)terminal of the communication terminal 154, and the communicationcontrol FET 180 may be configured with a first communication control FET182 and a second communication control FET 184, which are configured onthe first and second paths, respectively.

Each of the first and second communication control FETs 182 and 184 iscontrolled in the same state through one signal from the MCU 140, andfor convenience of explanation, they will be described as thecommunication control FET 180 in the following description. Thecommunication control FET 180 may be on/off controlled by thecommunication control FET block unit 146 of the MCU 140 described above.

More specifically, when an overdischarge determination signal isoutputted from the overdischarge determination unit 144, thecommunication control FET block unit 146 may sense this and generate acommunication control FET off signal and output it to the communicationcontrol FET 180. Accordingly, the communication control FET 180 iscontrolled to be off so that the current flow between the MCU 140 andthe communication terminal 154 may be blocked.

At this time, as the overdischarge determination signal is generated andoutputted, the AFE 130 outputs a discharge FET off signal for blockingthe flow of the discharge current, so that the communication control FEToff signal is outputted a predetermined time earlier than the dischargeFET off signal.

For example, although not shown separately in the drawings, aconfiguration such as a delay buffer is arranged between the AFE 130 andthe discharge FET 170 to output a communication control FET off signal,and after a predetermined time delay, a discharge FET off signal may beoutputted to the discharge FET, or to generate an overdischargedetermination signal in the MCU 140 and to output the overdischargedetermination signal to the AFE 130 after a predetermined period oftime, so that a communication control FET off signal may be outputtedfirst. The present invention is not limited to one specific method, andthe discharge FET 170 may be implemented in various manners that thecommunication control FET 180 may be shut off after a predetermined timeafter it is first interrupted.

In such a way, the communication control FET 180 is configured to becontrolled in the same state as the discharge FET 170, so that it ispossible to prevent the dangerous situation that the surge currentgenerated when the discharge current flow is blocked flows into thebattery pack through the communication path and destroys the MCU 140.

Although not described above, when the overdischarge state is released,that is, when the off-state discharge FET 170 and the communicationcontrol FET 180 are turned on, the two FETs are controlled in the samestate, and the order is controlled in the order of the discharge FET170->the communication control FET 180, which is inverse to theoverdischarge state. This will be described in detail in the followingdescription of the operation step.

Here, the predetermined time may be set to, for example, 250 ms.

FIG. 2 is a block diagram showing operation steps of a control circuitof a battery pack according to the present invention.

First, a state determination step (S100) for monitoring the voltagestate of each battery cell and determining the overcharge oroverdischarge state of the battery cells is operated. As described withreference to FIGS. 1 and 2, as the AFE 130 monitors the voltage state ofeach battery cell and transfers information on it to the MCU 140, theMCU 140 may determine whether the battery cells 110 are overcharged oroverdischarged using the preset overcharge determination value and theoverdischarge determination value.

As described above, if the MCU 140 determines that the battery cell 110is overdischarged, an overdischarge protection step S200 for performinga protection operation of the battery cell for the overdischargeoperates.

The overdischarge protection step S200 may operate in the order of anoverdischarge determination signal output step S210, a communicationcontrol FET block step S220, and a discharge FET block step S230.

More specifically, if it is determined through the state determinationstep S100 that the battery cells are in the overdischarge state, inorder to prevent the battery cells from being discharged, an operationfor blocking current from flowing from the battery cells 110 to theoutput terminal 152, that is, the external load of the external system200, must be performed. Therefore, if the MCU 140 determines that thebattery cell is in the overdischarge state, an overdischargedetermination signal output step S210 for generating and outputting anoverdischarge determination signal to the AFE 130 is operated.

At this time, the communication control FET block unit 146 of the MCU140 senses that an overdischarge determination signal is generated andoutput and performs a communication control FET block step S220 forblocking the communication control FET 180 on the communication path.

More specifically, the communication control FET block unit 146 sensesthat an overdischarge determination signal is generated and outputted,generates a communication control FET off signal, and outputs it to thecommunication control FET 180 to turn off the communication control FET180. Therefore, it is possible to interrupt the current flow in thecommunication path between the MCU 140 and the external system 200.

After the communication control FET block step S220 is operated, adischarge FET block step S230 for blocking the discharge current flow tothe charge/discharge path between the battery cells 110 and the outputterminal 152 is operated.

More specifically, the AFE 130 receiving the overdischarge determinationsignal from the MCU 140 recognizes it as a command to block the flow ofthe discharge current, and generates a discharge FET off signal thatturns off the discharge FET configured on the charge/discharge pathbetween the battery cells 110 and the output terminal 152 (P−).

At this time, the generated discharge FET off signal is not outputteddirectly to the discharge FET 170, but after the communication controlFET block step S220 is operated, then outputted to turn off thedischarge FET 170.

As described above, for example, a configuration such as a delay buffermay be disposed between the AFE 130 and the discharge FET 170, and inthe system configuration of the AFE 130, through various methods foroutputting it after a predetermined time after the generation of thedischarge FET off signal, the discharge FET 170 may be blocked after thepredetermined time after the communication control FET 180 is turnedoff.

That is, during the overdischarge protection operation, the current flowon the communication path is firstly blocked by using the communicationcontrol FET 180 before turning off the discharge FET 170 by isolatingthe communication path with the external system 200, so that after thecurrent is prevented from flowing instantaneously into the communicationpath, the flow of discharge current is blocked.

Thus, when the discharge FET is turned off in such a way, that is, thesurge current generated by interrupting the discharge current flow isprevented from destroying the MCU 140 through the communication path, itis possible to protect the MCU 140, which may further improve the safetyof the battery pack.

Here, the predetermined time may be set to, for example, 250 ms.

After the overdischarge protection step S200 of the battery cellsoperates as described above, an overdischarge release determination stepS300 for determining whether the overdischarge protection state isreleased, that is, the overdischarge is determined to be restored to anormal state, by monitoring the voltage state of each battery cell, andan overdischarge release step S400 for canceling the overdischargeprotection operation when it is determined that the overdischargeprotection state is released are performed.

After overdischarge protection operation, the MCU 140 determines whetherthe overdischarge state is released by comparing the voltage state ofthe battery cells with a predetermined overdischarge determination value(S300).

Therefore, the MCU 140 generates an overdischarge release signal andoutputs the overdischarge release signal to the AFE 130, and the AFE 130receiving it recognizes the flow of the blocked discharge current as acommand to release it, and generates and outputs a discharge FET onsignal, so that a discharge FET block release step S410 for releasingthe discharge FET block is operated.

Meanwhile, the MCU 140 may sense that a discharge FET on signal isoutputted, and in order to release a blocked communication path, mayrelease the communication control FET block by generating and outputtingthe communication control FET on signal. That is, current flow mayproceed in the communication path between the MCU 140 and the externalsystem 200 (S420).

Here, as in the overdischarge protection step, there is a certain timeinterval between the discharge FET control and the communication controlFET control.

That is, as the MCU 140 detects the output of the discharge FET ONsignal and generates and outputs a communication control FET ON signal,this is because the communication control FET block release step S420 isoperated after the discharge FET block release step S410, and the timeinterval is set in advance so that two steps operate at predeterminedtime intervals. The predetermined time may be set to, for example, 250ms.

As a result, it may be described that the overdischarge protection stepS200 and the overdischarge release step S320 are operated in reverseorder as described above.

More specifically, in the overdischarge protection step S200, after thecommunication control FET is first turned off (S220), it is configuredto turn off the discharge FET (S230) after a predetermined time.

On the other hand, in the overdischarge release step S320, after thedischarge FET is first turned on (S322), it is configured to turn on thecommunication control FET after a predetermined time (S324).

That is, during overdischarge protection, the communication path isfirstly isolated/blocked before blocking the discharge current flow, andwhen the overdischarge is released, the discharge FET is controlled tobe turned on so that the discharge current flows, and the current flowsin the communication path, so that the surge current generated when thedischarge current flows is blocked through the communication path toprevent the MCU 140 from being destroyed.

Through such a step configuration, the discharge FET 170 and thecommunication control FET 180 are controlled to be in the same state(on/off), and during the discharge current block, the order of turningoff is in the order of the communication control FET 180->the dischargeFET 170. When the discharge current block is released, turning on iscontrolled in the order of the discharge FET 170->the communicationcontrol FET 180. As the flow of discharge current blocks, it is possibleto prevent the surge current from flowing into the battery pack throughthe communication terminal 150 and adversely affecting the MCU 140, sothat a battery pack with improved stability may be provided.

On the other hand, although the technical idea of the present inventionis specifically described with reference to the above embodiments, itshould be noted that the above embodiments are for the purpose ofexplanation and not for the purpose of limitation. It will be apparentto those skilled in the art that various modifications and variationsmay be made in the present invention without departing from the spiritand scope of the invention.

1. A battery pack comprising: a cell balancing unit for balancing aplurality of battery cells; an analog front end (AFE) for monitoring avoltage state of each of the battery cells and controlling the cellbalancing unit; a microcomputer unit (MCU) for controlling the AFE basedon a voltage state of each battery cell monitored by the AFE; and anexternal terminal connected to the battery pack and an external system.2. The battery pack of claim 1, wherein the external terminal comprises:an output terminal for allowing a current to flow between the batterycell and the external system; and a communication terminal for enablingcommunication between the MCU and the external system.
 3. The batterypack of claim 2, further comprising: a charge field effect transistor(FET) for blocking current flow from the output terminal to the batterycell; and a discharge FET for blocking current flow from the batterycell to an output terminal, which are configured on a current pathbetween the battery cell and the output terminal.
 4. The battery pack ofclaim 3, wherein the charge FET and the discharge FET are turned on/offby the AFE.
 5. The battery pack of claim 4, wherein a communication pathis formed between the MCU and the communication terminal, and acommunication control FET for blocking a path between the communicationterminal and the MCU under a control of the MCU is configured on thecommunication path.
 6. The battery pack of claim 5, wherein the MCUcomprises: an overcharge determination unit for generating an overchargedetermination signal and outputting the overcharge determination signalto the AFE, when it is determined that the battery cell is overcharged;an overdischarge determination unit for generating an overdischargedetermination signal and outputting the overdischarge determinationsignal to the AFE, when it is determined that the battery cell isoverdischarged; and a communication control FET block unit for detectingthat the overdischarge determination signal outputted from theoverdischarge determination unit and outputting a communication controlFET off signal to the communication control FET to block a current flowbetween the MCU and the communication terminal.
 7. The battery pack ofclaim 6, wherein when the overcharge determination signal is inputtedfrom the MCU, the AFE outputs a charge FET off signal to block a flow ofa charge current, and when an overdischarge determination signal isinputted, the AFE outputs a discharge FET off signal to block a flow ofa discharge current.
 8. The battery pack of claim 7, wherein thedischarge FET off signal is outputted after a predetermined time afterthe communication control FET off signal is outputted.
 9. A method ofcontrolling a battery pack including battery cells, the methodcomprising: a state determination step of monitoring a voltage state ofeach battery cell to determine an overcharge or overdischarge state ofbattery cells, wherein when it is determined that the battery cells areoverdischarged in the state determination step, an overdischargeprotection step is operated, wherein the overdischarge protection stepcomprises: an overdischarge determination signal output step ofoutputting an overdischarge determination signal to an AFE to block aflow of a discharge current; a communication control field effecttransistor (FET) block step of blocking a communication control FETconfigured on a communication path between the battery pack and anexternal system; and a discharge FET block step of blocking a flow of adischarge current from the battery cells to an external terminal. 10.The method of claim 9, further comprising, after the operation of theoverdischarge protection step, an overdischarge release determinationstep of monitoring the voltage state of each battery cell to determinewhether overdischarge of battery cells is released, wherein when it isdetermined that the overdischarge state of the battery cells isreleased, an overdischarge release step of releasing an overdischargeprotection state of the battery cells is operated, wherein theoverdischarge release step comprises: a discharge FET block release stepof generating and outputting a FET on signal to release the dischargeFET block; and a communication control FET block release step ofgenerating and outputting the communication control FET on signal torelease the communication control FET block, wherein the communicationcontrol FET block release step is operated a predetermined time afterthe discharge FET block release step is operated.
 11. The method ofclaim 9, wherein the discharge FET block step is operated apredetermined time after the communication control FET block step isoperated.